Artificial limb



Oct. 26, 1954 c. H. BENNINGTON ETAL 2,692,392

ARTIFICIAL LIMB Filed April 5, 1951 FIG. l.

Slwentor CHARLES H. BENN/NGTUN Mm n L L mf .0 E7 M Patented Oct. 26,1954 UNITED STATS ATENT OFFICE ARTIFICIAL LIME Application April 5,1951, Serial No. 219,386

7 Claims. l

This invention has to do with an artificial limb and in particular withan artificial limb having an ankle and foot capable of simulating manyof the movements of a natural limb.

In normal walking the foot has at least six different movements: dorsaland plantar flexion, pronation and supination in the hind foot, andflexion in both directions of the metatarsals and toes in the forefoot.The problem of providing an artiicial limb capable of all thesemovements is an old one, and ball and socket joints, bearings, springs,connections of various resilient materials and many other suggestionshave been made for simulating the natural movements. The commonestobjections to prior artificial limbs have been their inability toperform in a manner comparable to a natural foot, and to stand up underthe heavy wear and strain to which they are subjected.

An object of the present invention is to provide in an articial limb arugged, simple connection between the parts representing the shin boneor tibia and the foot, permitting the foot to be moved in a mannerclosely resembling that of a natural foot. This object is attained byproviding a block of resilient material having rigid plates embeddedtherein and flexibly connecting the tibia to the foot.

According to other features of the invention the metatarsal section ismade flexible, and a heel cord is provided which can be readily adjustedto vary its tension.

rlihese and other features of the invention will be more fully describedin connection with the drawings, in which:

Fig. l is a side elevation showing a limb according to the invention;

Fig. 2 is a side elevation of the limb partly in section; and

Fig. 3 is perspective of the pantala-r articulation according to theinvention.

Referring to Fig. 2, a foot member lil is made from any suitable hard,relatively light material, such as wood. The anterior portion of thefoot has two slots il and lia. Slot l is at a point in the footcorresponding to the break at the base of the metatarsal and slot liacorresponds to the break at the toe joint. Slot IIa is approximately 25%wider at its opening or top il than slot i I, thereby permitting thefoot in walking to roll forward to approximate the natural fiexion atthe respective joints. In an articial foot for the average male adult,slot II will be e across the opening and slot IIa wide. A cavity I3 inmidtarsal section I4 and a cavity l in toe sec- 2 tion I'l register witha hollow portion metatarsal I2. An elongated resilient member I8, ofrubber or the like, is loosely inserted in cavities I3 and I t andhollow portion I5. The portion of member I8 lying in metatarsal I2 has acon-cavity d8a to insure firm anchoring of rubber IS in cavities I3, I5and l5 during walking. A pliable sole I9 recessed in the midtarsalsection M and toe section il', is secured with the resilient member i8to the midtarsal, metatarsal and toe sections lli, I2 and Ilrespectively by means of screws 2li or the like.

The pantalar articulation comprises a block ZI of resilient material,preferably natural or synthetic rubber, such as that used in first lineautomobile tires. While block 2l will here and in the claims be referredto as being made of rubber, it is understood that any other materialhaving resilient characteristics such as rubber could be used. Bypantalar is meant the joints and tissues surrounding the talus. The termpantalar articulation is used to describe an element which can be movedto simulate most of the movements of the talus and oscalcis. Theresiliency of'rubbei' block 2| should be about the same throughout, butthe resiliency of each block should preferably vary depending on theage, weight and activity of the wearer of the limb. For instance, in thecase of a` normally active adult of 200 pounds for whom the limb beingdescribed will be considered, the block should have a durometer readingof 50.

Referring to Fig. 3, the upper surface of block 2l is V-shaped andconsists of front portion 22 and rear portion 23 which slope towards theopposed lower horizontal surface. Preferably front portion 22 isslightly, about 12%, longer than. rear portion 23. By way of examplesome of the dimensions of block 2I are as follows:

(d) Narrowest distance between upper and lower` surfaces (e) Maximumdistance between portion 22 and lower surface 115e- (f) Maximum distancebetween portion 23 andlower surface ha;

(g) Width at juncture of portions 22 and The angle which portions 22 and23 (the legs of the V) make with one another is determined by thethickness of rubber required between the l5 in upper and lower surfacesof block 2|. This will vary as previously pointed out with the weight,age and activity of the wearer of the limb. However, in all cases it isdesirable to keep this thickness to a minimum in order to insure thatthe pivoting point of the leg will be as close to the foot as possibleas in the natural pantalar joints.

A thin plate 24, of the order of 116 thick, of metal or other rigidmaterial, e. g. bronze, is bonded into block 2| just below and parallelto the surfaces of portions 22 and 23. Plate 24 is preferably one piecewhich has been bent to conform the V-shaped upper surface of the block.

Another plate 25, similar to plate 24, is bonded into block 2| justabove and parallel to its flat lower surface. Two bolts 26 are brazed toplate 25 and project therefrom. Two bolts 21 are brazed to the front ofplate 24 and project therefrom as do two other bolts 28 brazed to therear of plate 24.

Bolts 25, 21 and 28, respectively, serve as the means for fasteningblock 2| to the foot and leg, and plates 24 and 25 the means foranchoring the bolts in the block. While other fastening and anchoringmeans are possible according to the invention, it is important that theconnection between the leg and foot be secure yet not rigid.

The bonding of plates 24 and 25, with their respective bolts extendingtherefrom, into block 2| may be done in any one of a number of wellknown ways.

In the embodiment of the invention here illustrated, plate 24 is about11g" in thickness and plate 25, g3g thick. Plate 25 is preferably madeof slightly heavier stock than plate 24 because it is fastened to thefoot by only two bolts 26, whereas plate 24 is fastened to the leg byfour bolts 21, 28. While both plates are substantially co-extensive withtheir parallel block surfaces and are embedded in the block about M3from the nearest outside surface, they could be at a greater or a lesserdistance therefrom. The plates could also be merely bonded or otherwisefastened to the upper and lower surfaces of the block. The importantpoint is to guard against thefplates being torn away from the block as aresult of the heavy strain to which they are subjected during use of theartificial leg. Embedding them is one good way of preventing this.

The leg, tibia or shin bone is divided into a hollow upper portion 3|and a lower portion 32 which telescopes into portion 3|. By means ofbolts 33 and flange 34 on upper portion 3| the position of lower portion32 may be adjusted therein to vary the length of the leg depending onthe requirements of the wearer. Base 35 of portion 32 is V-shaped tocorrespond to upper surfaces 22 and 23 of block 2|. It will be noted'that edge 36 of front portion 22 extends beyond base 35 because frontportion 22 is slightly, about 12%, longer than rear portion 23. Thereason for making front portion 22 longer than rear portion 23 is thatin plantar exion the front of block 2| undergoes greater strain and muststretch more than in dorsal flexion, because in the latter the heel cordacts as a restraint.

Suitable holes to accommodate bolts 26 extend through foot lil andterminate in cut-out 31 in the bottom of foot l0. Nuts 38 may be screwedonto the ends of bolts 26 and work against a plate 39 to hold the blocksecurely on the foot. Similarly, holes extending through base 35 permitbolts 21 and 28 to extend therethrough and the block is securely held tothe lower portion of the tibia by nuts 40.

It will be appreciated that an important feature of block 2| is that itprovides in a single, relatively inexpensive unit a pantalararticulation where heretofore a plurality of complicated parts wasnecessary. Furthermore, block 2| may be easily replaced with anotherblock by the wearer if it becomes Worn or breaks.

A heel cord 42 is connected between a hook 43 formed on bracket 44secured to the posterior of tibia portion 32 and an adjustable screwmechanism in the heel of the foot. The adjustable screw mechanismoperates in a hole 45 extending through the bottom of heel 46 andcontains an internally threaded flanged bushing 41 having holes 4B inits flanged end whereby bushing 41 may be turned by means of a Spannerwrench or key (not shown). Ends 49 of cord 42 are secured in anexternally threaded ferrule 50 and held therein by an anchored pin 5|which rests against shoulder 52 in pipe 55. Threaded members 41 and 50cooperate so that when member 41 is turned the tension on heel cord 42will be varied. It is important that the wearer of the artificial limbcan easily adjust the tension of the heel cord himself without recourseto others.

While I have shown cord 42 as made from fibrous material with a leathercovering 53, it may be made from any other suitable inelastic material.

It will be appreciated that the metatarsal section, pantalararticulation and heel cord here described combine to provide anartificial limb whose foot portions mechanically simulate many of themovements of a natural foot. While any one of the three above describedimprovements may be incorporated individually in an artificial limb, thecombination of all three of these constitutes an important feature ofthe invention.

Terms such as tibia, foot, heel, etc. used in the claims designatemechanical simulations which perform some of the functions of thenatural members.

What is claimed is:

1. In an artificial foot, 'two slots of different widths in the frontportion of said foot defining a metatarsal section, a hole through saidmetatarsal section and cavities registering therewith in the toe andmidtarsal sections of the foot on either side of the metatarsal, and ap-iece of flexible material extending through said hole and cavities.

2. An artificial foot comprising a toe, a metatarsal and a midtarsalsection, a first slot between said toe and metatarsal sections, a secondslot narrower than said first slot between said metatarsal and midtarsalsections, a hole in said metatarsal registering with cavities in the toeand midtarsal sections, and a piece of flexible material extendingthrough said hole and cavities whereby in walking the front portion ofthe foot simulates some of the movements of a natural foot.

3. In an artificial limb, a pantalar articulation connected between thetibia and the foot comprising a block of rubber having a V-shaped uppersurface and a relatively fiat lower surface, the upper surfacecontacting the tibia member and divided into a front and a rear portionsloping towards the lower surface, the front portion being of the orderof 12% longer than the rear portion, the lower surface of said blockcontacting the foot member, a first metal plate embedded in said blockjust below and parallel with the upper surface, a second metal plateembedded in the block just above and parallel with the lower surface,fastening means projecting from both said plates for fastening saidblock to the tibia and foot members, a heel cord connected between saidtibia and the heel portion of said foot, and an adjustable screw in ahole in the bottom of the heel connecting said cord to the heel wherebythe tension exerted by said cord may be Varied.

4. In an artificial limb, a leg member having an upper portion and alower portion telescoping therein to adjust the length of said leg, afoot member, a pantalar articulation between said last two mentionedmembers comprising a block of automobile tire grade rubber having anupper surface contacting the lower leg member and divided into front andrear portions angularly disposed with respect to each other to resemblea V, said front portion being of the order of 12% longer than said rearportion and extending said amount free from said lower leg member whenthe upper surface of the block is in contact therewith, the lowersurface of said block being substantially flat and contacting the footmember, a rst bronze plate embedded in said block just below andparallel with the upper surface, a second bronze plate embedded in theblock just above and parallel with the lower surface, bolts extendingfrom both of said plates for fastening said block to the leg and foot, aheel cord of relatively inelastic material connected between the lowerrear portion of said leg and the heel of the foot, an adjustable screwmechanism in a hole in the bottom of the heel for connecting the cord tothe heel whereby tension exerted by said cord may be varied, the frontportion of said foot being divided by two slots into a metatarsal, amidtarsal and a toe section, the anterior of said slots being of theorder of 25% wider at its top than Isaid posterior slot, a hollowportion extending through said metatarsal section and cavitiescorresponding therewith in said midtarsal and toe sections, a piece ofrubber extending through said cavities and hollow portion and having aconcavity in the portion in the metatarsal, and a sole of pliablematerial covering the bottom of said foot portions through which saidpiece of rubber extends.

5. An artificial foot comprising complementary toe, metatarsal andmidtarsal sections having angular end faces disposed in spaced, end toend relation, each of said sections being recessed inwardly of itsbottom face, a block of resilient material common to said sectionsdisposed in said recesses in section spanning relation, a yieldable solemember recessed in said toe and midtarsal sections in overlying relationto said resilient material, and a plurality of screws securing said solemember and said block of resilient material to said toe, metatarsal andmidtarsal sections.

6. The invention according to claim 5, and in which the surface juncturebetween said metatarsal section and said block of resilient material isat least in part concavo-convex.

7. In an artincial limb, the combination of a longitudinally adjustableleg member terminating in a il-shaped end portion, a foot memberincluding a toe section and a metatarsal section yieldably connectedthereto in spaced end to end relation, a pantalar connection betweensaid V- shaped end portion and said foot member comprisms a block ofresilient material having a horizontal bottom face and a complementaryV- shaped upper face, a plurality of oppositely extending stud screwsbonded in said block securing it to said V-shaped end portion and tosaid foot member, a rearwardly extending hook member secured to Saidadjustable leg member, a shouldered, internally threaded bushingrevolvably seated in the heel portion of said foot member ush therewith,and a looped cord having its free ends secured in an externally threadedferrule adjustably connected to and between said hook member and saidbushing.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 809,875 Wilkins Jan. 9, 1906 2,315,795 Johnson et al. Apr. 6,1943 2,475,373 Catranis July 5, 1949 FOREIGN PATENTS Number Country Date7,781 Great Britain Apr. 1, 1909 308,671 Germany Oct. 22, 1918 326,131Germany Sept. 24, 1920 625,528 Great Britain June 29, 1949

